Those varieties are hardy here - that is why Reinder's markets them here.
I have heard more than a few guys on here say that slice overseeding with a majority KBG will not achieve very good results as germination takes so long and the seedlings are more apt to get choked right out by the existing stand of turfgrass. I need something that will emerge and be vigorous. I do agree with your rye assessment and I always mix in 20% rye or so.